Anaerobic Methane Oxidation in Freshwater Environments

Abstract

Anaerobic methane oxidation was long thought to be limited to marine environments. Meanwhile, anaerobic methane oxidation coupled to denitrification, carried out by Candidatus “Methylomirabilis oxyfera”-like bacteria and Candidatus “Methanoperedens nitroreducens”-like archaea, has been discovered in various freshwater environments. Furthermore, this process even has been identified as the major methane sink in some environments such as lakes and peatlands. Anaerobic methane oxidation with sulfate or with oxidized iron and manganese species might also take place in freshwater environments, but the organisms mediating these reactions are unknown, and data on these processes at low salinities are scarce. In addition, a clear distinction between sulfate- and metal-dependent anaerobic methane oxidation has not been possible in most environments. In general, there is not much data available on the importance of anaerobic methane oxidation in freshwater habitats, but the available studies – in concert with molecular detection and quantification of anaerobic methane oxidizing organisms in a variety of freshwater habitats – indicate that anaerobic methane oxidation in freshwater environments could be a globally important methane sink.

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